The mineral clouds on HD 209458b and HD 189733b

Abstract

ABSTRACT3D atmosphere model results are used to comparatively study the kinetic, nonequilibrium cloud formation in the atmospheres of two example planets guided by the giant gas planets HD 209 458b and HD 189 733b. Rather independently of hydrodynamic model differences, our cloud modelling suggests that both planets are covered in mineral clouds throughout the entire modelling domain. Both planets harbour chemically complex clouds that are made of mineral particles that have a height-dependent material composition and size. The remaining gas-phase element abundances strongly effects the molecular abundances of the atmosphere in the cloud forming regions. Hydrocarbon and cyanopolyyne molecules can be rather abundant in the inner, dense part of the atmospheres of HD 189 733b and HD 209 458b. No one value for metallicity and the C/O ratio can be used to describe an extrasolar planet. Our results concerning the presence and location of water in relation to the clouds explain some of the observed differences between the two planets. In HD 189 733b, strong water features have been reported while such features are less strong for HD 209 458b. By considering the location of the clouds in the two atmospheres, we see that obscuring clouds exist high in the atmosphere of HD 209 458b, but much deeper in HD 189 733b. We further conclude that the (self-imposed) degeneracy of cloud parameters in retrieval methods can only be lifted if the cloud formation processes are accurately modelled in contrast to prescribing them by independent parameters.

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

“…We chose a hierarchical approach of modelling environments where we utilise 97 1D profiles extracted from the 3D GCM calculated for the cloud-free HAT-P-7b (Mansfield et al 2018) and apply our kinetic cloud formation model consistently linked to an chemical equilibrium code. Our study is the continuation of previous investigations of cloud formation in the giant gas planets HD 189733b and HD 209458b (Lee et al 2015a;Helling et al 2016;Lee et al 2016;Lines et al 2018b), and the super-hot gas giant WASP-18b in order to enable a comparative overview for these two classes of giant gas planets given that observations mainly provide snapshots of certain aspects (e.g. presence of certain gas species, existence of clouds, a hot spot off-set) of each of these planets so far.…”

Results from a set of three-dimensional numerical experiments of a hot Jupiter atmosphere

“…Our results have shown that the super-rotating equatorial jet, found as a solution for hot Jupiter atmospheres from several models (see for example Cooper & Showman 2005;Menou & Rauscher 2009;Rauscher & Menou 2010;Heng et al 2011;Dobbs-Dixon & Agol 2013;Parmentier et al 2013;Showman et al 2015;Helling et al 2016;Kataria et al 2016;Lee et al 2016), is robust in our setup. Our model does not include a drag or friction at the bottom boundary potentially responsible for removing some of the dependence on initial conditions (see Liu & Showman 2013;Cho et al 2015).…”

Dynamic mineral clouds on HD 189733b

“…However, Fe[s] rich grains are expected to reside below the photosphere of HD 189733b (Lee et al 2015;Helling et al 2016a), where they would have negligible effects on the observable scattered and emitted light.…”

“…This is converted into a mass opacity by the relation κ sca,H 2 (λ) = n H 2 σ sca,H 2 (λ)/ρ gas . The abundance of molecular H 2 (n H 2 [cm −3 ]) is calculated at each cell assuming chemical equilibrium using the routines from Helling et al (2016a).…”